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Arctic sea ice reaches historic summer low

September 16, 2010 | 12:30
pm

Scientists have recorded the third-lowest level of summer Arctic sea ice since data collection began more than 30 years ago.

The National Snow and Ice Data Center, which uses satellite imagery to track the so-called summer minimum, said the Arctic ice sheet had reached its minimum on Sept. 10, and that it was headed back into its winter growth cycle.

The minimum this year, however, was 25% below a 31-year average (1979-2010), a deficit of 625,000 square miles.

NSIDC reported:

This is only the third time in the satellite record that ice extent has fallen below 5 million square kilometers (1.93 million square miles), and all those occurrences have been within the past four years. The minimum for 2009 was 5.10 million square kilometers (1.97 million square miles), fourth lowest in the satellite record.

Despite a late start to the melt season, the ice extent declined rapidly thereafter, with record daily average ice-loss rates for the Arctic as a whole for May and June. Assuming that we have indeed reached the seasonal minimum extent, 2010 would have the shortest melt season in the satellite record, spanning 163 days between the seasonal maximum and minimum ice extents.

Declining seasonal sea ice sheets have had a deadly effect on the polar bear, which was given federal endangered species protection in 2008 -- the first species to be listed explicitly as a victim of climate change.

-- Geoff Mohan

Photo: A mother polar bear and cubs on the shore of Hudson Bay, near Churchill, Manitoba, Canada. Credit: Jonathan Hayward/AP